Motivated by these results, we report here a comprehensive DFT+\(U\)  investigation including spin-orbit effects of the structural, electronic and magnetic properties of the double perovskite (DP) SCIO as a function of strain in comparison to the end members SCO and SIO. Our results confirm the semimetallic ground state of SrIrO\(_3\) . SrCoO\(_3\)  has a ferromagnetic metallic ground state in close proximity to an AFM insulating state, whereas SCIO emerges as an AFM insulator. The relaxed structures of SCO, SIO and SCIO, shown in Fig. REF , exhibit substantial octahedral rotations and tilts. In contrast to the Co\(^{4+}\)  and Ir\(^{4+}\)  electron configuration in the end members SCO and SIO, detailed analysis indicates a noticeable charge transfer from Ir to Co resulting in Co\(^{4-\delta }\)  in the intermediate-spin state (IS) and an Ir\(^{4+\delta }\)  configuration in the double perovskite SCIO, reminiscent of the charge transfer recently reported in SrMnO\(_3\) /SrIrO\(_3\) (001) superlattices [1]}. We note that the DP itself can be regarded as a superlattice containing alternating SrCoO\(_3\)  and SrIrO\(_3\)  layers in the (111)-direction. Furthermore, we explored the role of biaxial strain, by varying the lateral lattice constant from the one of NdGaO\(_3\)  (compressive), through SrTiO\(_3\)  (unstrained) to GdScO\(_3\)  (tensile). A subtle strain effect is observed in the orbital occupation and the band gap. Moreover, we have calculated the optical properties within the independent-particle (I.P.) picture, as well as by considering quasiparticle effects within the \(GW\)  approximation (single shot \(G_{0}W_{0}\) )[2]} and excitonic effects by solving the Bethe-Salpeter equation (BSE)[3]}, [4]}.
Changes of the in- and out-of-plane component of the real and imaginary part of the dielectric constant as a function of the lateral lattice parameter reflect the effect of strain. The calculated absorption coefficients are compared with transmission measurements on SCIO samples grown on different substrates using the MAD technique.
